The Wood Glossary is a guide to lumber terminology used on Texas Woodcrafts and other wood-related sites. You'll see definitions for common terms used in describing wood, as well as some terms specific to our unique Texas woods.
Air-dried lumber - Lumber that was dried, usually outside, to an equilibrium moisture content with the air it was exposed to. Any lumber below 30% moisture content is classified as air dried.
Angel Step - Angel Step or Angel Stairs is a figure pattern found in lumber cut from trees that have twisted trunks, and is common in maples and walnuts. The figure on the board is characterized by short, delicate curls progressing up the board on a tangent, starting and ending out of nowhere - the image of a spiral staircase. The figure goes around the log; to achieve that image on the face of the board, the log should be flat sawn.
Annual growth rings - The layer of wood growth put on a tree during a single growing season. The annual growth rings of many species (e.g., oaks and pines) are readily distinguished because of differences in the cells formed during the early and late parts of the season. In some temperate zone species (black gum and sweetgum) and many tropical species, annual growth rings are not easily recognized.
Bandmill/band sawmill - An evolution in sawmill technology that uses a thinner band saw blade (less kerf therefore less sawdust waste) than a circular saw.
Bark pocket (Bark inclusion) - 1) A bark-filled blemish, crack or hole in the board. 2) An opening between annual growth rings that contains bark. Bark pockets appear as dark streaks on radial surfaces and as rounded areas on tangential surfaces.
Bastard grain - Annual rings on an angle at or near 45° to the wide face of a piece of lumber.
Beams and stringers - Large pieces (nominal dimensions, 5" and thicker, width more than 2" greater than thickness, e.g. 5 by 8 inches and up) of rectangular cross section graded with respect to their strength in bending when loaded on the narrow face.
Bevel - Lumber cut at an angle or slant.
Bevel siding - A lumber pattern with a flat face, a thin edge, and a thick edge.
Bird peck - A small hole or patch of distorted grain resulting from birds pecking through the growing cells in the tree. In shape, bird peck usually resembles a carpet tack with the point towards the bark; bird peck is usually accompanied by discoloration extending for considerable distance along the grain and to a much lesser extent across the grain.
Birdseye figure - Small localized areas in wood with the fibers indented and otherwise contorted to form few to many small (BB sized) circular or elliptical figures remotely resembling birds' eyes on the tangential (plain-sawn) surface. Sometimes found in sugar maple and used for decorative purposes; rare in other hardwood species.
Blue Stain - A bluish or grayish discoloration of the sapwood caused by the growth of certain dark-colored fungi on the surface and in the interior of the wood; made possible by the same conditions that favor the growth of other fungi. Particularily noticable in pines and significantly reduces the value of a log for milling or processing.
Board - Lumber that is nominally less than 2 inches thick and 2 or more inches wide. Boards less than 6 inches wide are sometimes called strips.
Board foot - A unit of measurement of lumber represented by a board 1 foot long, 12 inches wide, and 1 inch thick or its cubic equivalent (144 cubic inches). In practice, the board foot calculation for lumber 1 inch or more in thickness is based on its nominal thickness and width and the actual length. Lumber with a nominal thickness of less than 1 inch is calculated as 1 inch.
Bookmatch - A term in veneering or sawing whereby successive pieces of veneer or boards, from a flitch or log, are arranged side by side. A properly done bookmatch will resemble a mirror image of the opposite side. Other names are sisters, butterflies, and mirrors.
Bound water - Water found within the cell wall of wood.
Bow - (1) The distortion of lumber in which there is a deviation, in a direction perpendicular to the flat face, from a straight line from end-to-end of the piece. (2) A deviation flat-wise from a straight line drawn from end to end of a piece, measured at the point of greatest distance from the straight line; it does not include short kinks.
Boxed Heart - The term used when the pith falls entirely within the four faces of a piece of wood anywhere in its length.
Burl - (1) Bulges and irregular growths that form on the trunks and roots of trees. Burls are highly sought after for the incredible veneer they yield and are used in turning as well. (2) A hard, woody outgrowth on a tree, more or less rounded in form, usually resulting from the entwined growth of a cluster of adventitious buds. Such burls are the source of the highly figured burl veneers used for purely ornamental purposes. (3) In lumber or veneer, a localized severe distortion of the grain generally rounded in outline, usually resulting from overgrowth of dead branch stubs, varying from 1/2 inch to several inches in diameter; frequently includes one or more clusters of several small contiguous conical protuberances, each usually having a core or pith but no appreciable amount of end grain (in tangential view) surrounding it.
Butt joint - A woodworking joint where the edges of two boards are placed against each other.
Cambium - The live, actively growing, layer of a tree. The cambium is one cell thick and resides between the sapwood and the phloem. It repeatedly divides itself to form new wood end causes the tree to grow and expand. It is the layer that becomes either bark or wood and lies dormant in the winter.
Cant Hook - A device used for rolling cants or logs. Many people mistake a cant hook for a peavey. The difference is that a cant hook doesn't have a point on the end like a peavey.
Cants - (1) Large planks or timbers cut on the head saw for further sawing elsewhere. (2) A log that has been slabbed on one or more sides. Ordinarily, cants are intended for resawing at right angles to their widest sawn face. The term is loosely used. Synonymous with flitch.
Carbide - A compound of carbon and other materials that is super hard. There are various grades of carbide depending on the application. In saw teeth they are brazed to the saw blade and ground to the proper configuration. These teeth are very hard and stay sharp longer than other types of teeth but, have a tendency to be brittle.
Carving quality - the ease which a species can be carved. This may be directly related to the hardness.
Poor: Extremely difficult to carve.
Case hardening - A condition of lumber in which it contains varying degrees of stress at different depths below the surface, causing it to cup when resawed or worked. Case hardening is caused when a board is dried too fast. The outer layers in a case-hardened board are compressed while the inner layers are in tension.
Cell - (1) The smallest, microscopic structure in wood. (2) A general term for the anatomical units of plant tissue, including wood fibers, vessel members, and other elements of diverse structure and function.
Cellulose - The carbohydrate that is the principal constituent of wood and forms the framework of the wood cells.
Center match - Lumber that has been worked with a tongue exactly in the center on one edge of each piece and a groove on the opposite edge to provide a close tongue-and-groove joint by fitting two pieces together.
Chamfer - A bevel or slope created by slicing off the square edge or end of a piece of wood or other material.
Chatoyance - A changeable color or luster. Wood appears to shimmer when moved.
Check - A separation of the wood normally occurring lengthwise of a piece across the rings of annual growth and usually as a result of seasoning (drying). A checked piece of wood has splits which develop lengthwise across the growth rings. Checking may occur at any time in the life of a piece of furniture, and is usually traceable to a sudden change in temperature and or humidity.
Chipped grain - Consists of a part of the surface being chipped or broken out in particles below the line of cut; it should not be classed as torn grain.
Circle Sawmill - A machine that uses a flat thin disk with teeth cut into the outer edge to saw wood, plastic, metal, or other materials.
Clear - A term including the higher grades of lumber - sound, relatively free of blemishes.
Close-grained wood - (1) Wood with narrow and inconspicuous annual rings; the term is sometimes used to designate wood having small and closely spaced pores, but in this sense the term "fine textured" is more often used. (2) Wood with more than six rings per inch.
Coarse-grained wood - (1) Wood with wide and conspicuous annual rings; that is, rings in which there is considerable difference between springwood and summerwood; the term is sometimes used to designate wood with large pores, such as oak, ash, chestnut, and walnut, but in this sense the term "coarse textured" is more often used. (2) Wood with less than four rings per inch.
Collapse - Irregular shrinkage in wood above the fiber saturation point caused by collapse of wood cells as free water is drawn out of the cell cavities without replacement with air or more water.
Common grade lumber - Lumber with obvious defects.
Compartment kiln - A kiln in which the total charge of lumber is dried as a single unit. It is designed so that, at any given time, the temperature and relative humidity are essentially uniform throughout the kiln. The temperature is increased as drying progresses, and the relative humidity is adjusted to the needs of the lumber.
Compound cut - An angled cut to both the edge and face of a board.
Compression wood - Abnormal wood that often forms on the lower side of branches and of leaning trunks of softwood trees: compression wood is identified by its relatively wide annual rings, usually eccentric, and its relatively large amount of summerwood, usually more than 50 percent of the width of the annual rings in which it occurs. Compression wood shrinks excessively lengthwise as compared with normal wood.
Conditioning - The exposure of a material to the influence of a prescribed atmosphere for a stipulated period of time or until a stipulated relation is reached between material and atmosphere.
Conifers - The botanical group of trees having needles, or scale-like leaves, and cones: they are usually "evergreen."
Crook - A deviation edgewise from a straight line drawn from end to end of a piece and measured at the point of greatest distance from the straight line: it does not include short kinks.
Cross grain - Grain not parallel with the axis of a piece; it may be either diagonal or spiral grain or a combination of the two.
Crotch - In lumber, a piece of wood taken from the fork of a tree. Crotch wood is highly valued for its figuring.
Cup - A curve in a piece across the grain or width of a piece; it is measured at the point of greatest distance from a straight line drawn from edge to edge of a piece. The board warps up like the letter U.
Curly-grained wood - Wood in which the fibers are distorted so that they have a curled appearance, as in "birdseye" wood. The areas showing curly grain may vary up to several inches in diameter.
Custom drying - Drying other people's lumber.
Custom milling - Surfacing or remanufacturing other people's lumber on order.
Custom sawing - Sawing of lumber under contract, usually to given specifications.
Cut stock - Clear pieces that have been ripped and cross cut from shop type lumber, such as stiles, rails, muntins, window sash, and many others, intended for further manufacture.
Cut-full lumber - Lumber intentionally manufactured in larger than normal thickness and width, usually to allow for shrinkage: a term sometimes confused with "full cut" lumber.
Cuttings - In hardwoods, portions of a board having the quality required by a specific grade or for a particular use. Obtained from a board by crosscutting or ripping.
Dark grain - Grain which is darker than the rest and should not be confused with pitch streaks.
DBH (Diameter Breast Height) - The diameter of a tree at breast height (4.5 feet above ground), together with the estimated height of the usable logs in a tree is used to determine the volume of lumber likely to be yielded in a log depending on the log scale used
Decay - Decay is disintegration of wood due to the action of wood-destroying fungi: the words "dote" and "rot" mean the same as decay.
Advanced decay - The older stage of decay in which the destruction is readily recognized because the wood has become punky, soft, and spongy, stringy, ringshaked, pitted, or crumbly. Decided discoloration or bleaching of the rotted wood is often apparent.
Decayed knot - A knot which, due to advanced decay, is not so hard as the surrounding wood.
Deciduous - Generally trees that have broad leaves that are shed in the fall. Usually it is a hard wood.
Defect - An irregularity found in a board that lowers its strength and value. Common defects are knots, staining, checks, etc.
Density - As usually applied to wood of normal cellular form, density is the mass of wood substance enclosed within the boundary surfaces of a wood-plus-voids complex having unit volume. It is variously expressed as pounds per cubic foot, kilograms per cubic meter, or grams per cubic centimeter at specified moisture content.
Diagonal grain - Annual rings at an angle with the axis of a piece as a result of sawing at an angle with the bark of the tree or log. A form of cross-grain.
Diffuse-porous wood - Certain hardwoods in which the pores tend to be uniform in size and distribution throughout each annual ring or to decrease in size slightly and gradually toward the outer border of the ring.
Dimension - Hardwood or softwood lumber, a term generally applied to lumber when the nominal size is 2 inches thick and 2 or more inches wide. The National Grading Rule for Softwood Dimension Lumber defines "dimension" as lumber from 2 through 4 inches thick and 2 inches and wider.
Dimension parts - A term largely superseded by the term "hardwood dimension lumber." It is hardwood stock processed to a point where the maximum waste is left at the mill, and the maximum utility is delivered to the user. It is stock of specified thickness, width, and length or multiples thereof. According to specification it may be solid or glued up, rough or surfaced, semi-fabricated or completely fabricated.
Dimensional Stability - a measure of movement in service when the wood is subjected to moderate changes in humidity. Descriptions include:
Discoloration - Changes in the color of wood which affect only its appearance.
Domestic - Lumber that grows in the United States.
Dog - 1) A device used to hold a log in place on the sawmill while it is being sawn. 2) that critter that gets underfoot when you are trying to work in your shop!
Dote - "Dote," "doze," and "rot" are synonymous with "decay" and are any form of decay which may be evident as either a discoloration or a softening of the wood.
Double end trimmed - Both ends cut reasonably square by a saw.
Dressed - Surfaced with a planer.
Dressed and matched - Lumber that has been worked with a tongue off center on one edge of each piece and a groove on the opposite edge to provide a close joint by fitting two pieces together.
Dressed size - The dimensions of lumber after being surfaced with a planing machine. The dressed size is usually 1/2 to 3/4 inch less than the nominal or rough size. A 2x4-inch stud, for example, actually measures about 1 1/2 by 3 1/2 inches.
Dry - Seasoned, usually to a moisture content of less than 19%.
Dry kiln - An enclosed chamber in which temperature and humidity conditions are subject to control for the purpose of drying lumber.
Dry rot - A term loosely applied to many types of decay but especially to that which, when in an advanced stage, permits the wood to be easily crushed to a dry powder. The term is actually a misnomer for decay, since all fungi require considerable moisture for growth.
Durability - A general term for permanence or lastingness: frequently used to refer to the degree of resistance of a species or of an individual piece of wood to attack by wood-destroying fungi under conditions that favor such attack: in this connection the term "resistance to decay" is more specific.
Earlywood - The portion of the annual growth ring that is formed during the early part of the growing season. It is usually less dense and weaker mechanically than latewood.
Edge - The narrow face of a rectangular-shaped piece of lumber.
Edge grain - Lumber sawed parallel with the pith of the log and approximately at right angles to the growth rings; that is, the rings form an angle of 45° or more with the wide face of the piece (also known as quarter-sawn).
Edge-grained lumber - Lumber that has been sawed so that the wide surfaces extend approximately at right angles to the annual growth rings. Lumber is considered edge grained when the rings form an angle of 45° to 90° with the wide surface of the piece (also known as quarter-sawn lumber).
Edge joining - Smoothing and squaring the edge of a board so that it can be glued up squarely to another piece.
Encased knot - A knot whose rings of annual growth are not intergrown with those of the surrounding wood.
End check - A surface check at the end of a piece of lumber.
Endgrain sealer - A paint-like material applied to the end grain of wood to stop it splitting (such as commercial “Anchorseal” or home-spun alternative like old paint, roofing tar, etc). This slows the loss of moisture thru the more-porous endgrain of the wood, to reduce the differential drying stresses and slow (or hopefully stop) the development of radial checks in the endgrain while the wood is drying. Used on logs while awaiting sawing or parting into turning blanks, turning blanks while awaiting rough-out, and rough-turned bowls (and other turnings) while undergoing final drying prior to finish-turning.
End-grained wood - The grain as seen on a cut made at a right angle to the direction of the fibers (e.g., on a cross section of a tree).
End-match - To tongue and groove the ends of matched lumber.
End-split - A lengthwise separation of the wood fibers at the end of a piece of lumber.
Equilibrium moisture content (EMC) - The moisture content at which wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature. The point at which the level of moisture in a board is equal to the moisture in the surrounding air. Wood is constantly attempting to lose or gain moisture to achieve equilibrium with its present environment. This moisture exchange maybe slowed, but not stopped, regardless of the finishes or sealers.
Export sale - Sale of lumber to be shipped to a foreign country.
Extractives - Substances in wood, not an integral part of the cellular structure, that can be dissolved out with hot or cold water, ether, benezene, or other relatively inert solvents.
Face - The wide surface of a piece of lumber; the wide surface showing the better quality or appearance from which a piece is graded.
Face-side - The wide surface used in grading showing the better quality or appearance.
Face-width - The width of the face of any piece of lumber; in tongued or lapped (rabbeted) lumber, it does not include width of tongue or lap.
Feather crotch figure - Figure resembling a cluster of feathers that is commonly found in the segment where a fork or crotch in the tree occurs. An alternate name is "flame figure"
Fiddleback-grained wood - Figure produced by a type of fine wavy grain found, for example, in species of maple; such wood being traditionally used for the backs of violins.
Figure - A distinctive pattern in wood created by its grain, annual rings, medullary and color variations (or deviation from regular, straight or symmetrical grain patterns). Types of figure includes: bear claw, birds-eye, burl, crotch, flame, fiddleback, curly, quilted, and ribbon stripe.
Finger-joint - Pieces of lumber machined on the ends and bonded together with glue. The joint is similar to slipping the fingers of two hands together. Also called end-joint or glue-joint.
Finish - Coatings of varnish, lacquer, wax, etc., applied to wood surfaces to protect and enhance their durability or appearance.
Finishing - The process of applying a finish to wood. Often includes multiple stages of sanding prior to application of a finish.
Finishing characteristics - Terminology to indicate how well the wood accepts a clear finish. Open-grained woods generally finish better than woods with large gum or resin deposits.
Poor: Does not finish well, some conditioning needed.
Finish lumber - A term indicating the higher grades of lumber, sound, relatively free of blemishes.
Finished size - The net dimensions after surfacing.
First and Seconds (FAS) - The top grade for hardwoods.
Flame figure - A grain pattern resembling flames which is commonly found in the wood in the area where two limbs diverge (a crotch or fork). An alternative name is Feather crotch figure.
Flat-grained wood - Lumber that has been sawed parallel to the pith and approximately tangent to the growth rings. Lumber is considered flat grained when the annual growth rings make an angle of less than 45° with the surface of the piece (also known as plain-sawn or slash-grain lumber).
Flitch - (1) A thick piece of lumber with or without wane (bark) on one or more edges suitable for remanufacturing. (2) A portion of a log sawn on two or more faces - commonly on opposite faces leaving two waney edges. When intended for resawing into lumber, it is resawn parallel to its original wide faces. Or, it may be sliced or sawn into veneer, in which case the resulting sheets of veneer laid together in the sequence of cutting are called a flitch. The term is loosely used. Synonymous with "cant".
Flooring - A lumber pattern with smooth face and tongue and groove edges.
FOG Wood – “Found on ground” - Wood of convenience, commonly unidentified and used when you have nothing better to use!
Foot - A unit of lineal measurement usually used to indicate the length of lumber.
Free water - Moisture found in the cell cavities of wood.
Full-cut lumber - Lumber that in thickness and width measures fully up to specified sizes: a term sometimes confused with "cut-full" lumber, the latter meaning lumber intentionally manufactured in larger than nominal thickness and width.
Fungus stain - Lumber stain caused by fungus growth in wood: fungi can be either of the sapwood-staining or decay-producing types.
Girth - The distance around a tree; the circumference.
Grade - The designation of the quality of wood; applied to lumber, plywood, logs, etc.
Grading rules - A set of criteria by which to judge various pieces of lumber or panels in terms of strength, appearance, and suitability for various uses. Regional grading agencies draw up rules for grading based on the voluntary product standards issued by the U.S. Bureau of Standards.
Grain - The direction, size, arrangement, appearance or quality of the fibers in wood. Among the many types of grain are fine, coarse, straight, curly, open, flat, vertical, and spiral.
Green lumber - (1) Freshly cut lumber that has not had time to dry. Lumber that is above 30% moisture content. (2) An alternate definition: lumber with a moisture content of 19% or more.
Green wood - Unseasoned wood (freshly sawn or unseasoned wood). Wood that has become completely wet after immersion in water would not be considered green, but may be said to be in the "green condition."
Growth ring - The layer of wood growth put on a tree during a single growing season. The annual growth rings of many species (e.g., oaks and pines) are readily distinguished because of differences in the cells formed during the early and late parts of the season. In some temperate zone species (black gum and sweetgum) and many tropical species, annual growth rings are not easily recognized.
Gum - A comprehensive term for nonvolatile viscous plant exudates, which either dissolve or swell up in contact with water. Many substances referred to as gums, such as pine and spruce gum, are actually oleoresins.
Hard hardwoods - Hardwood species with an average specific gravity greater than 0.50, such as oaks, hickories, or hard maples. See also "soft hardwoods".
Hardness - The property of wood that is indicated by a resistance to cutting, scratching, denting, pressure or wear. Generally the higher the density, the harder the wood. Also related to the hardness is the ease of which nails or screws can be driven into the wood.
Very Soft: Very easily dented.
Hardwood - A general term referring to any variety of broad-leaved, deciduous trees, and the wood from those trees. The term has nothing to do with the actual hardness of the wood; some hardwoods are softer than certain softwood (evergreen) species.
Heart rot - Any rot characteristically confined to the heartwood. It generally originates in the living tree.
Heart shake - A shake or crack radiating out from the heartwood. See also "radial crack" and "check".
Heart stain - A discoloration of the heartwood.
Heartwood - The dead inner core of a tree between the pith to the sapwood. Heartwood may be infiltrated with gums, resins, and other materials which usually make it darker and more decay-resistant than sapwood.
Hollow Pith - Term for the condition of a log where the small central core or pith of the log or tree is hollowed out. This is usually related to ants but gives the appearance of decay. One major problem with hollow pith is a tendency for decay to form around the pith. Hollow pith also complicates (or enhances) the use of a piece of wood for turning on a lathe.
Honeycomb - 1) Pits or spots in wood caused by fungi. It develops in the living tree and does not develop further in wood in service. 2) a defect in wood created by improper drying, resulting in cellular separation in the interior of a piece of wood, usually along the wood rays (internal splits or collapse that cannot be seen on the surface).
Imported - Lumber that doesn't grow in the United States.
Infeed - The direction a work piece is fed into a blade or cutter.
Incipient decay - The early stage of decay in which the disintegration has not proceeded far enough to soften or otherwise perceptibly change the quality of the wood (See spalting).
Intergrown knot - One partially or completely intergrown on one or two faces with the growth rings of the surrounding wood.
Interlocked-grained wood - 1) Grain in which the fibers put on for several years may slope in a right-handed direction, and then for a number of years the slope reverses to a left-hand direction, and later changes back to a right-handed pitch, and so on. Such wood is exceedingly difficult to split radially, though tangentially it may split fairly easily.
Joist - Pieces (nominal dimensions 2 to 4 inches in thickness by 5 inches and wider) of rectangular cross section graded with respect to strength in bending when loaded on the narrow face: used as supporting members under a floor or over a ceiling.
Juvenile wood - Wood formed early in the life of a tree. By most measures, juvenile wood is lower in quality than wood that forms later; this is particularly true of the softwoods. Juvenile wood shrinks and swells along the grain as moisture content changes. Strength is lower, and in some cases much lower, than mature wood of the same tree
Kiln - In lumber drying, a kiln is a room or building where temperature, moisture, and the air circulating are controlled to dry wood.
Kiln dried - Lumber which has been dried under conditions of controlled temperatures and humidities in a dry kiln.
Knot - A branch or limb embedded in a tree and cut through in the process of manufacturing. Knots are classified according to size, quality and occurrence. In lumber, the size classifications are: Pin knot, one not over 1/2-inch in diameter; Small, a knot larger than 1/2-inch but not over 3/4-inch; Medium, larger than 3/4-inch but not over 1 1/2-inches; Large, over 1 1/2-inches in diameter. The shape of the knot as it appears on a cut surface depends on the angle of the cut relative to the long axis of the knot.
Knot cluster - Two or more knots grouped together as a unit with the fibers in the wood deflected around the entire unit.
Laminated wood - A piece of wood built up of plies or laminations that have been joined either with glue or with mechanical fastenings: the term is most frequently applied where the plies are too thick to be classified as veneer and when the grain of all plies is parallel.
Latewood - The part of a tree's annual growth ring that is formed later in the season
Lath - A thin, narrow wooden strip, used as a backing for wall plaster or other materials.
Light sap stain - A slight difference in color which will not materially impair the appearance of a piece if given a natural finish.
Lignin - The second most abundant constituent of wood, located principally in the secondary wall and the middle lamella, which is the thin cementing layer between wood cells. Chemically, it is an irregular polymer of substituted propylphenol groups, and thus no simple chemical formula can be written for it.
Linear foot - A measurement of the length of a board in one dimension; this is not the same as a board foot which is a volumetric measurement.
Log - A portion of a trunk (or stem) of a felled tree that has been cleared of branches and made ready for sawing into lumber.
Loose knot - A knot that is not held firmly in place by growth, shape, or position and that cannot be relied upon to remain in place.
Loosened or raised grain - Consists of a small portion of the wood being loosened or raised but not displaced.
Lumber - A manufactured product derived from a log in a sawmill, or in a sawmill and planing mill, which when rough shall have been sawed, edged and trimmed at least to the extent of showing saw marks in the wood on the four longitudinal surfaces of each piece for its overall length, and which has not been further manufactured other than by cross-cutting, ripping, resawing, joining crosswise and/or endwise in a flat plane, surfacing with or without end matching, and working.
Lumber tally - A record of lumber giving the number of boards or pieces by width, thickness, length, grade and species.
Machine burn - A darkening of the wood due to overheating by the machine knives or rolls when pieces are stopped in a machine.
Manufacturing defects - Includes all defects or blemishes that are produced in manufacturing, such as chipped grain, loosened grain, raised grain, torn grain, skips in dressing, hit and miss (series of surfaced areas with skips between them), variation in sawing, miscut lumber, machine burn, machine gouge, mismatching, and insufficient tongue-and-groove.
Matched - Lumber that has been worked with a tongue on one edge of each piece and a groove on the opposite edge to provide a close tongue-and-groove joint by fitting two pieces together; when end-matched, the tongue and groove are worked in the ends also.
Medium grain - Wood with 4 to 6 rings per inch.
medullary rays - A structure in a tree that stores and delivers food horizontally through the trunk. In some species, such as oak, the medullary rays can be quite large. When the tree is quartersawn, the rays become visible on the face of the board. This feature is also known as “ray flecks.”
Mill Marks - Small parallel ripples or ridges produced on the surfaces or edges of wood by cutting tools. In the case of saws, virtually all saw blades or chainsaws produce mill marks.
Mill-run - Lumber that is in varying widths and grades.
Millwork - Generally wood remanufactured in millwork plants; it includes such items as inside and outside doors, windows and door frames, blinds, porch-work, mantels, panel work, stairways, mouldings, and interior trim; it does not include flooring, ceiling, or siding.
Mineral streak - An olive to greenish-black or brown discoloration of undetermined cause in hardwoods.
Mixed grain - Lumber may be both vertical and flat grain.
Modified wood - Wood processed by chemical treatment, compression, or other means (with or without heat) to impart properties quite different from those of the original wood.
Modulus Of Rupture (MOR) - A measure of the breaking strength of the wood. The higher the MOR, the greater the force required to break it.
Very Weak: Very easily broken.
Modulus Of Elasticity (MOE) - A measure of how stiff the wood is. This measures how much force is required to bend a small, clear, straight-grained specimen at a span ratio of 14/1 according to American Society of Testing Material standard D 255-70.
Very Pliant: Very easily bent.
Moisture content - The moisture content of wood is the weight of the water in wood expressed as a percentage of the weight of the wood from which all water has been removed (oven dry). Moisture is removed from lumber either by air drying or by use of special drying kilns.
Nail / Screw Holding - A measure of how well the wood holds fasteners when a force is applied to the fastener.
Poor: Nails/screws easily pulled out.
Natural characteristics - Characteristics which occur naturally in a tree as it grows, as apparent in a piece of lumber.
Natural Defects Defects that result from how a tree grows such as knots, decay, wind shake, radial cracks, bird peck, etc.
Nominal measure - The "board measure" contents of lumber when calculated from measurements of named sizes; same as gross measure.
Nominal size - As applied to timber or lumber, the size by which it is known and sold in the market. This often differs from the actual size.
Old growth - (1) Biologically, a stand of timber that is near its climax; such trees may be 200 years old or more. In timber management planning, old growth also refers to timber that is older than the rotation age planned for future forests; this definition may include trees that are 100 years of age, or less. (2) Timber in or from a mature, established forest. When the trees have grown during most if not their entire individual lives in active competition with their companions for sunlight and moisture, this timber is usually straight and relatively free of knots.
Open-grained - Common classification for woods with large pores, such as oak, ash, chestnut, and walnut: also known as "coarse textured."
Outfeed - The side of a power tool where the board exits. The opposite of infeed.
Oven-dried weight -The weight of a piece of lumber that has been dried, under high temperatures, in an oven until it is devoid of all water. Used to calculate the moisture content of wood.
Oven-dry wood - Wood completely dried until it is without any moisture content.
Patterned lumber - Lumber that is shaped to a pattern or to a molded form in addition to being dressed, matched, or shiplapped, or any combination of these workings.
Peavey - A tool used for rolling logs. Similar to a cant hook, but it has a point on the end.
Peck - Pockets or areas of disintegrated wood caused by advanced stages of localized decay in the living tree. It is usually associated with cypress and incense cedar. There is no further development of peck once the tree is seasoned.
Phloem - The inner part of a tree's bark that delivers water and other nutrients.
Photosynthesis - A process that plants use to synthesize nutrients from water end minerals, using light.
Piling - Round timber of any required size or length, usually used with smaller end in the ground.
Pin hole - From any cause approximately 1/16" in diameter.
Pin knot - A knot that is not more than 1/8 inch in diameter.
Pitch - An accumulation of resin.
Pitch pocket - An opening extending parallel (commonly) to the annual rings of growth usually containing, or which has contained, pitch, either solid or liquid. Most commonly found in wood from conifers (softwood), though can be found in some kinds of hardwood, such as cherry and Mesquite.
Pitch seam - Shake or check which is filled with pitch.
Pitch streak - A well-defined accumulation of pitch in the wood cells in a more or less regular streak. Most common in conifers.
Pith - The small, soft core occurring near the structural center of a tree trunk, branch, twig, or log, around which the annual rings form..
Pith fleck - A narrow streak, resembling pith on the surface of a piece; usually brownish, up to several inches in length; results from burrowing of larvae in the growing tissues of the tree.
Plain-sawn lumber - A method of sawing lumber where the log is cut tangential to the growth rings. Another term for flat-grained lumber; especially common in softwood lumber.
Plank - (1) A piece of lumber, from 2 but not including 5 inches thick, generally used with wide face horizontal: (differs from joist only that latter is used on edge). (2) A broad board, usually more than 1 inch thick, laid with its wide dimension horizontal and used as a bearing surface.
Plywood - A glued wood panel made up of relatively thin layers of veneer with the grain of adjacent layers at right angles, or of veneer in combination with a core of lumber or of reconstituted wood. The usual constructions have an odd number of layers.
Pocket - A pocket is a well-defined opening between the rings of annual growth, usually containing pitch or bark.
Pocket rot - Advanced decay which appears in the form of a hole, pocket or area of soft rot usually surrounded by apparently sound wood.
Pole - Round timber of any required size or length, usually used with larger end in ground.
Porous wood - Wood with larger than normal pores and vessels
Posts and timbers - Large pieces (nominal dimensions, 5" by 5" and larger, width not more than 2" greater than thickness) of square or approximately square cross section graded primarily for use as posts or columns.
Preservative - Any substance that, for a reasonable length of time, will prevent the action of wood-destroying fungi, borers of various kinds, and similar destructive life when the wood has been properly coated or impregnated with it.
Progressive kiln - A kiln in which the total charge of lumber is not dried as a single unit but as several units, such as kiln truckloads, that move progressively through the kiln. The kiln is designed so that the temperature is lower and the relative humidity higher at the end where the lumber enters than at the discharge end.
Pulp Trees - Small trees and saplings that will be ground to produce paper. Lumber farmers often over-plant their acreage and remove smaller trees for pulp as the crop matures.
Quarter - A unit of measure for the nominal thickness of hardwood, expressed in quarters of an inch. Generally expressed as a proper or improper fraction,such as 4/4 or 6/4. For example 4/4 (stated "four quarters") lumber has a nominal thickness of one inch, though the final measured thickness is usually somewhat less after the lumber has been dried and planed. Similarly, 8/4 lumber is nominally 2 inches thick, and so on.
Quarter-sawn - A method of cutting lumber where the annual rings are relatively perpendicular to the face of the board. Quarter-sawn lumber tends to be more dimensionally stable than other forms of lumber, such as plane-sawn. Quarter-sawn lumber as also referred to as edge-grained lumber.
Quilted Figure - Small-scale “pillow”-like figure most commonly found in Oregon Big-leaf Maple.
Radial - Coincident with a radius from the axis of the tree or log to the circumference: in a round timber or piece of lumber, a line or surface extending outward from the heart-center: a radial surface is always edge-grain.
Radial section - A lengthwise section in a plane that passes through the centerline of the tree trunk.
Radial shrinkage - Shrinkage in a piece of lumber that occurs across the growth rings as it begins to dry.
Ray - (1) Strips of cells extending radially within a tree and varying in height from a few cells in some species to 4 or more inches in oak. The rays serve primarily to store food and transport it horizontally in the tree. On quartersawed oak, the rays form a conspicuous figure, sometimes referred to as flecks. (2) A ribbon like figure caused by the strands of cells which extend across the grain in quarter-sawn lumber.
Reaction wood - (1) Abnormal wood tissue that was formed in a leaning tree. Reaction wood is very unstable and prone to warping and cupping when sawn into lumber. (2) Wood with more or less distinctive anatomical characters, formed typically in parts of leaning and crooked stems and in branches. In hardwoods this consists of tension wood and in softwoods of compression wood.
Relative humidity - The amount of moisture in the air is measured as a percentage of the total amount of moisture the air can hold at a particular temperature. This is known as relative humidity. The ideal relative humidity for a home is between 35% and 45%, too much above or below these levels problems can begin to occur.
Resaw - A board split in half from a thicker board.
Ripcut (ripping) - A cut made parallel to the grain of a board.
Rotary-cut veneer - Veneer which was cut from a log in one long sheet. Rotary cut veneer is cut from a log like a roll of paper towels.
Rough-sawn - (1) Lumber that is either green or dried that has not been dressed. (2) Lumber that has been sawn, edged, and trimmed, but not surfaced.
Sap - The water in a tree which is rich in minerals and nutrients.
Sapwood - The new wood in a tree that lies between the bark and the heartwood. Sapwood is usually lighter in color, and becomes heartwood as the tree ages. Under most conditions the sapwood is more susceptible to decay than heartwood.
Saw kerf - (1) Grooves or notches made in cutting with a saw; (2) that portion of a log, timber, or other piece of wood removed by the saw in parting the material into two pieces.
Seasoning - The process of removing the moisture from green wood to improve its workability and stability. Also called "drying". See air dried, kiln-dried, and kiln.
Seasoning (Air-Dried) - Dried by exposure to air, usually in a yard, without artificial heat.
Seasoning (Kiln-Dried) - Dried in a kiln with the use of artificial heat.
Second growth - Timber that has grown after the removal, whether by cutting, fire, wind, or other agency, of all or a large part of the previous stand.
Selects - In softwood, lumber which has been graded strictly for its appearance. In hardwood, lumber which is one grade below first and second.
Shake - A separation along the grain, the greater part of which occurs between the rings of annual growth. Usually considered to have occurred in the standing tree or during felling rather than a product of drying (see “Wind Shake").
Shaving - A small wood particle of indefinite dimensions developed incidental to certain woodworking operations involving rotary cutterheads usually turning in the direction of the grain (such as lathe turning). This cutting action produces a thin chip of varying thickness, usually feathered along at least one edge and thick at another and generally curled.
Shear - A condition of stress or strain where parallel planes slide relative to one another.
Shipping-dry lumber - Lumber that is partially dried to prevent stains and mold in transit.
Shrinkage - The percentage reduction in size of wood when it goes from green to dry. Wood shrinks differently in all directions, and specific shrinkage values can be obtained from the Louisiana Forest Products Laboratory or from the Wood Handbook. The values listed represent general relationships. This measure can also be used to estimate swelling when moisture is added.
Volumetric % Tangential % Radial %
Sidebend - A distortion of a board in which there is a deviation edgewise from a straight line from end to end of the board.
Side-grained wood - Another term for flat-grained or plain-sawn lumber.
Side lumber - A board from the outer portion of the log-ordinarily one produced when squaring off a log for a tie or timber.
Slab - In a sawmill operation, a slab is the piece of wood cut off a log that is round on one side and flat on the other. These are produced from the first cuts on logs and the edging of flitches. They can be used for firewood, siding, or can be processed into lumber if large enough. The term is also commonly used for a very thick flitch cut from the log for possible use as a bench, table-top or mantle.
Slash-grained wood - Another term for flat-grained or plain-sawn lumber.
Soft hardwoods - Hardwood species with an average specific gravity less than 0.50, such as cottonwoods, basswoods, or willows. See also "Hard Hardwoods".
Soft rot - A special type of decay developing under very wet conditions (as in cooling towers and boat timbers) in the outer wood layers, caused by cellulose-destroying microfungi that attack the secondary cell walls and not the intercellular layer.
Softwoods - Generally lumber from a conifer such as pine or cedar. The name softwood does not refer to the density or hardness of the wood. There are some hardwoods which are softer than some softwoods.
Sound - A term referring to a board which has no or very few defects which will effect its strength
Sound knot - A knot that is solid across its face, at least as hard as the surrounding wood, and shows no indication of decay.
Spalting - A by-product of the rotting process that is carried out by a vast array of stain, mold and decay fungi, that are found naturally on the forest floor. When the temperature and humidity are right, spalting can cause many different and beautiful patterns in rotting wood. The unusual colouration may be due to chemically induced reactions between the wood, fungi and insect deposits, often resulting in black, pink, grey and multicoloured streaked wood. Spalting may also be induced in an unspalted piece of wood to enhance its beauty.
Species - A category of biological classification; a class of individuals having common attributes and designated by a common name. "Species" is always properly used with the "s" when referring to trees or other biological classifications.
Specific gravity - (1) The ratio of the weight of wood to an equal volume of water. The higher the specific gravity, the heavier the wood. (2) As applied to wood, the ratio of the ovendry weight of a sample to the weight of a volume of water equal to the volume of the sample at a specified moisture content (green, air-dry, or ovendry).
Spike knot - A knot cut approximately parallel to its long axis so that the exposed section is definitely elongated.
Spindle - A narrow, turned piece of wood.
Spiral-grained wood - Wood in which the fibers take a spiral course about the trunk of a tree instead of the normal vertical course. The spiral may extend in a right-handed or left-handed direction around the tree trunk. Spiral grain is a form of cross grain.
Split Resistance - A measures of how well the wood resists splitting from nailing. (Pilot holes can reduce the splitting.)
Poor: Splits very easily.
Stain - A discoloration in wood caused by a fungus, minerals or chemicals. A die or pigment used to discolor wood.
Sticker - A ľ" to 1" wood strip that is inserted between stacks of green wood and spaced between 16" to 24" to allow air to flow through the stack to ensure proper drying.
Straight-grained wood - Wood in which the fibers run parallel to the axis of a piece.
Stump-Shot Lumber - Lumber having jagged or irregular ends, sawn from a butt log.
Surfaced lumber - A piece of wood that has been planed smooth on one or more surfaces.
Surfacing - The process of planing lumber at the lumber mill in order to smooth one or more surfaces.
Tangential Shrinkage - Shrinkage in a piece of lumber that occurs along or parallel to the growth rings as it begins to dry.
Taper - A piece of wood that has been cut so that it is wider on one edge than the other.
Tension wood - Abnormal wood found in leaning trees of some hardwood species and characterized by the presence of gelatinous fibers and excessive longitudinal shrinkage. Tension wood fibers hold together tenaciously, so that sawed surfaces usually have projecting fibers, and planed surfaces often are torn or have raised grain. Tension wood may cause warping.
Texture - (1) A term often used interchangeably with grain. Sometimes used to combine the concepts of density and degree of contrast between earlywood and latewood. (2) Texture refers to the finer structure of the wood rather than the annual rings.
Timber - (1) A term used to describe wood, either standing or that has been processed for use (from the time trees are felled, to its end product as a material suitable for industrial use) as structural material for construction or wood pulp for paper production. Timbers may be used as beams, stringers, posts, caps, sills, girders, purlins, etc. (2) Felled trees that are nominally 5 or more inches in diameter.
Tongue and groove - A joinery method where one board is cut with a protruding "groove" and matching piece is cut with matching grove along its edge.
Trash metal - Debris (generally metallic) imbedded in a tree and typically not identified until the logs are being milled or turned. The end result is damaged blades (and sawyer's tempers)! Examples include barbed wire, fencing nails/staples, ceramic electrical insulators, horseshoes, bottles and the like.
Twist - Warping in lumber where the ends twist in opposite directions.
Unselected - Lumber that has a mix of heartwood and sapwood.
Veneer - A thin sheet of wood cut from a log or a thicker piece of lumber.
Vertical-grained lumber - Another term for edge-grained or quarter-sawn lumber.
Wane - Bark or lack of wood from any cause on edge or corner of a piece except for eased edges.
Warp - Any variation from a true or plane surface. Warp includes bow, crook, cup, and twist, or any combination thereof.
Wavy-grained wood - Wood in which the fibers collectively take the form of waves or undulations.
Weathering - The mechanical or chemical disintegration and discoloration of the surface of wood caused by exposure to light, the action of dust and sand carried by winds, and the alternate shrinking and swelling of the surface fibers with the continual variation in moisture content brought by changes in the weather. Weathering does not include decay.
White wood - Lumber sorted for the white sapwood. Usually refers to hard or soft maple.
Wood weight - The weight of wood measured in pounds per cubic foot at 12 percent moisture content. The more dense the wood, the heavier it is.
Wormholes - Holes and channels cut in wood by insects. Breakdown is:
Pin Worm Hole: One not over 1/16" in diameter.
Yard lumber - A little-used term for lumber of all sizes and patterns that is intended for general building purposes having no design property requirements.